1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same, and more particularly, to a non-volatile memory device allowing for multi-level cell operation and a method of fabricating the same.
2. Description of the Related Art
Non-volatile memory device, such as Electrically Erasable Programmable ROMs (EEPROMs) and flash memory devices, maintain the integrity of data stored in a memory cell irrespective of whether a supply of electric power is removed from the device. In contemporary systems, there is a continued progression from the use of optical disc or magnetic disc storage systems to the use of semiconductor device based storage. There is thus an increased need for flash memory based storage units. In such a flash memory unit, data is typically stored in a floating gate. Recently, however, a nitride layer has been employed as a charge trapping layer in a flash memory device with a Metal Oxide Nitride Oxide Silicon (MONOS) structure or a Silicon Oxide Nitride Oxide Silicon (SONOS) structure.
As the packing density of the flash memory devices continues to increase, studies have been carried out on the formation of a control gate within a semiconductor substrate. One example of this is provided in U.S. Patent Application Publication No. 2002-0071315, published Jun. 13, 2002, and entitled “Non-volatile Memory having embedded word lines”.